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The Moon is Earth's only natural satellite, orbiting at an average distance of 384 399 km (238,854 mi; 30 Earths across).It faces Earth always with the same side.This is a result of Earth's gravitational pull having synchronized the Moon's rotation period with its orbital period (lunar month) of 29.5 Earth days.
The Moon's heavily cratered far-side. The origin of the Moon is usually explained by a Mars-sized body striking the Earth, creating a debris ring that eventually collected into a single natural satellite, the Moon, but there are a number of variations on this giant-impact hypothesis, as well as alternative explanations, and research continues into how the Moon came to be formed.
The geology of the Moon (sometimes called selenology, although the latter term can refer more generally to "lunar science") is quite different from that of Earth. The Moon lacks a true atmosphere , and the absence of free oxygen and water eliminates erosion due to weather .
The Moon's elongation is its angular distance east of the Sun at any time. At new moon, it is zero and the Moon is said to be in conjunction. At full moon, the elongation is 180° and it is said to be in opposition. In both cases, the Moon is in syzygy, that is, the Sun, Moon and Earth are nearly aligned.
The "harvest moon" (also known as the "barley moon" or "full corn moon") is the full moon nearest to the autumnal equinox (22 or 23 September), occurring anytime within two weeks before or after that date. [18] The "hunter's moon" is the full moon following it. The names are recorded from the early 18th century. [19]
Blue Ghost also plans to capture high-definition imagery of a total eclipse as the Earth blocks the sun just before a lunar sunset ushers in frigid lunar night on March 16. Eric Lagatta covers ...
Schematic illustration of the internal structure of the Moon. Several lines of evidence imply that the lunar core is small, with a radius of about 350 km or less. [5] The diameter of the lunar core is only about 20% the diameter of the Moon itself, in contrast to about 50% as is the case for most other terrestrial bodies.
Lunar corona A solar corona up Beinn Mhòr (South Uist). In meteorology, a corona (plural coronae) is an optical phenomenon produced by the diffraction of sunlight or moonlight (or, occasionally, bright starlight or planetlight) [1] by individual small water droplets and sometimes tiny ice crystals of a cloud or on a foggy glass surface.